Antenna system



Jan. 18,1938. F. F. M'EaRlA-M j 2,105,925

ANTENNA SYSTEM Filed Aug. 25, 1934 2 Shets-Sheet 1 F/G/ RAD/0 R K vRECEIVE/P A 4 h" \GAP -//v WHICH /7 ICE COLLEC rs 5 I m/vmro/v F. F.MERE/AM A TTORNEV ANTENNA SYSTEM Filed Aug. 25, 1934 2 Sheets-Sheet 2Has INVENTOR F: F. MERR/A M ATTORNEY Patented Jan. 18, 1938 hairs RATENTGFFiQE ANTENNA SYSTEM Franc is Merriaiii, Montcl air, N. J., assignor toBell Telephone Laboratories, Incorporated, New York, N. In, acorporation of New York Application August 25 1934, Serial No. 741,356

Hi Claims.

This invention relates to antenna systems and more particularly to asystem and method of removing sleet 'or ice from antennae.

8 An object of this invention is to prevent the rormation bf sleet onantennae.

. Another obieet of this invention is to remove sleet on antennaeemployed in short wave radio systems automatically.

Another object of this invention is to disable a radio system whenabnormalities occur which result in the production of standing Waves onthe line between the transmitter and the antenna of the system;

In certain radio communication systems, espe- =cially those employed asan adjunct to land tele ph ne lines, repeaters and other remotelycontrolled stations are left unattended. During {cold weather, theantennae of these stations at. times accumulate considerable ice andsleet. The prese'nee of ice and sleet on antennae materially airects thequality of short and ultra-short wave transmission and reception emloyed on these systems.

In short and ultra shott wave radio systems, .iglf ly directive antennaeare employed. Ordiparity the impedance of the antennae and of the lineconnecting the transmitting apparatus to the antennae are balanced. Thisbalancing of impedahe'et at the junction point of the transmittingantenna and the line results in the more eihci'eht transfer of energy tothe antenna and in lower line losses. When this matching of imm'dance isdestroyed, standing wave voltages are produced on the line. The presenceof sleet on the antenna due to the variation in the capacity of theantennae and other causes changes the impedance relation at the junctionpoint of line and antenna.

In accordance with a feature of this invention, a source of heatingenergy responsive to the presence of standing Waves on the line isapplied to the antenna. This heating energy melts the sleet or icewhereby the standing wave voltage is removed from the line and thebalanced imped- ,ance relation at the junction point of line and antennais restored. When the standing Wave voltage is removed from the line,the antenna is no longer supplied by the heating source.

In one modification, the existence of standing Waves on the line betweenthe transmitter and the antenna, due to causes such as the breaking ofthe line, disables the transmitter.

In accordance with another feature of this invention, sleet or ice isremoved from an antenna by automatically supplying heating currentthrough the antenna intermittently as required. Whenever ice is formedon part of the antenna, the power current passes through the antenna andwhen the ice is melted on that part of the antenna, the power current isremoved.

A more comprehensive understanding of this invention may be obtained rbyreference to the drawings in which:

4 Fig. 1 is a schematic of a circuit embodying this invention in whichheating current is supplied to an antenna intermittently as requiredwhen sleet forms on the antenna;

Fig. 2 is a schematic of a circuit embodying this invention in whichalternating current is supplied to an antenna when standing waves areproduced between the transmitter and antenna of the system;

Fig. 3 is a schematic of a circuit embodying this invention in Whichheating current from a direct current source is applied to an antenna ofa radio system and in which the transmitter of the system is disabledwhen standing waves occur on the line between the transmitter andantenna of the system;

Fig. 4 is a representation of the voltage along the line leading from atransmitting apparatus to an antenna of the circuit shown in Figs. 2 and3 when no sleet or ice is formed on the antenna: and

Fig. 5 is a representation of the voltage along the same line as thatshown in Figs. 2 and 3 when sleet or ice forms on the antenna.

In Fig. 1, a radio transmitter or receiver, indicated as such-in therectangle, supplies or receives signaling energy to or from a closedcircuit antenna i of the rhombic type by means of an open wiretransmission line 2. A means for supplying heating energy to the antennacomprises an alternating current generator 4. The current passes fromthe generator through a current regulating rheostat 5, the primaryWinding of a transformer 3 and the armature and make contact of a relay6. From the secondary of transformer 3 the current passes to the line 2.A filter comprising a condenser shunted across the secondary. oftransformer 3 and a quarter wave length line 3 in series with thesecondary of transformer 3 is inserted between secondary of thetransformer 3 and the line 2. The filter comprising the condenser andquarter wave length line prevents the radio frequency power from thetransmitter from entering the circuits of the heating current source.This type of filter is described in a paper entitled Theoretical andPractical Aspects of Directional Transmitting The gap I! is located inthe system so that when.

atmospheric conditions are such that ice forms on the antenna, ice alsocollects in the gap It is preferable to locate the gap at a point whichis at low radio frequency potential. The cathode of device 9 isconnected through a potentiometer H] to one terminal of the generator 4.Connected across the output of the device 9 is a relay H in.

series with a resistance |2. The engagement of the armature of relay IIand its make contact results in the energization of thealternatingcurrent relay 6 from current supplied by the source 4. A condenser l3connected in series with the potentiometer I is shunted across the inputcircuit of device 9. Heating current is supplied to the filament ofdevice 9 by the generator 4 through a transformer |4.,,. The current forthe anode of device 9 is supplied from the generator 4 through aresistance l2 and winding of relay. Two condensers 5 and I6 arerespectively inserted in series with each side of the line 2 to preventthe alternating current from V the heating source, which is of course ofmuch lower frequency than the radio frequency signaling currents, fromdamagingthe radio apparatus. .A current limiting resistance 2| isconnected between the secondary of transformer 3 and the anode of device9.

A. half wavelength loop I8 is connected in series with theantenna IV andin parallel with a terminating resistance 9. This halfwave. length loopprovides a lowresistancepath for the lower frequency alternating currentemployed for heating the antenna wire around the terminating resistancewithout interfering with ,the function of the terminating resistance.

The operation of the circuit is as follows: Normally no appreciablecurrent passes in the output of device 9 due to the, negative bias onthe control electrode. This negative bias is produced by the impositionof part of the alternating electromotive force generated bythe source 4upon the rectifying circuitconsisting of condenser I3 and the controlelectrode and, cathode of .device 9. When ice or sleet forms on thewires of thetransmittingline 2, the ice gap I1 is closed and itsresistance is lowered to avalue which permits the negative charge toleak off the control electrode, or in other words substantially lowersthe negative bias of the control electrode of device 9. The width of thegap I1 is so proportioned that it is not closed by water during a rainstorm. The gap is preferably of the horntype asshown in. the drawings.The current in the output circuit of device 9 increases sufiiciently toenergize relay The engagement of the armature and contact of relay I Idue to this energization results in the actuation of relay 6 with theresulting engagement of the contact and armature of relay 6. Theactuation of, relay firesults in application of current from thegenerator 4 th ro ugh .th e transformer 3 and the lines 8.and 2 totheantenna I. This low frequency current melts the ice or sleet .on theantenna wires. Whenthetemperature of the antenna and line wires hasincreased sufficiently to causathe sleet or ice to melt, theice in thegap is also melted by the heat conducted from the transmission linewires to the gap and the gap opens. The opening of the gap results inthe normal negative bias being again impressed on the control electrodeof device 9. As a consequence, no appreciable current passes in theoutput of device 9. Relay H is deenergized and the source of heatingcurrent from source 4 is removed from the line by the disengagement ofthe make contact and armature of relay 6. The heating circuit isaccordingly restored to its normally inoperative condition.

The system shown schematically in Fig. 2 depends upon the existence ornon-existence of standing waves on the line leading from a radiotransmitter to an antenna. The system shown in this figure differs fromthe system shown in Fig. 1 mainly in respect to the principle employedfor turning the power on or off.

In Fig. 2 a radio transmitter indicated as such in the rectangle isconnected to an antenna 3| by means of a line 32. Two blockingcondensers 33 and 34 are inserted respectively in series with 1 eachside of the line 32. The heating current for melting the sleet or ice onthe antenna 3| is supplied by an alternating current generator 35through the primary winding of a transformer 36, the current regulatingresistance 3'! and the contact and armature of an alternating currentrelay 38. The secondary winding of the transformer 36 is connected tothe line 32 by means of a quarter wave length line 54. A condenser 39 isbridged across the line 54. The condenser 39 and the quarter wave lengthline serve as a filter for preventing the radio frequency power fromentering the heating system.

Between the blocking condensers 33and 34 and the radio transmitter, thecontrol electrodes of two space discharge devices 40 and 4| areconnected in push-pull relation. Two resistances 42 and 43 are connectedin series and shunted across the control electrode of devices 40 and 4|.The resistances 42 and 43 are connected directly across the line 32. Apotentiometer 44 connected to a unidirectional current source 45 isconnected between the common point of resistances 42 and 43 and thecathodes of devices 49 and 4|. The potentiometer 44 impresses asufiicient negative bias potential on the grids of devices 40 and 4| tonormally prevent their operation. Two relays 46 and 4! in series areconnected in the output circuit of devices 40 and 4 i. Aunidirectionalcurrent source 48 supplies the devices 40 and 4| with anode currentthrough relays 41 and 46 or through biasing resistance 49 and relay 45.The sensitivity of relay 41 is changed by varying the biasing resistance49. The cathodes of devices 49 and 4| are heated by current suppliedfrom the source 35 through a transformer 58. Two condensers 5| and 52are shunted across the cathode and anode of devices 46 and 4!,respectively.

A terminating resistance 3 is connected in series with the antenna 3 5.When this terminating resistance is connected in series with theantenna, the formation of sleet or ice on the antenna results in amismatch of impedances at the point of connection between antenna andline. This mismatch of impedances causes the production of standingwaves on the line, their amplitude depending upon the degree ofmismatch. A half wave length loop H3 in parallel with the resistance |9provides alow resistance path for the alternating current employed forheating .the antenna wire around the terminating resistance I9. Each ofthe leads connecting the control electrodes of devices 43 and ll to thetransmission line 32 and each of the leads of the half wave length loopI8 are connected respectively at electrically opposite points on thetransmission line 32 in order that the electrical symmetry of the line32 may not be disturbed.

The operation of the system shown in Fig. 2 may be more clearlyunderstood by reference to Figs. 4 and 5. The numeral designations shownin Figs. 4 and 5 are the same as those in Fig. 2. The dotted lineparallel to the line 32 of Fig. 4 represents the normal voltage existingalong the line 32 when the system is functioning properly. The dottedlines of Fig. 5 represent the existence of standing wave voltages alongthe line 32 when sleet forms on the antenna 3|.

In Fig. 2 normally just sufficient current passes in the output circuitof devices ll) and 4| so that the relay it is energized to prevent theengageent of its break contact with its armature. Relay G1, on the otherhand, is deenergized when the radio frequency voltage on thetransmission line 32 is normal (i. e. that represented by the dottedline in Fig. 4). The engagement of contact and armature of relay 41 orthe contact and armature of relay 4'6 results in the energization ofrelay 38. The energization of relay 33 results in the engagement of itscontact and armature. This action causes heating current from thegenerator 35 to be supplied to the antenna 3| through the transformer36, line 54 and line 32. When standing wave voltages such as thoseillustrated in Fig. 5 are produced on the line 32, either the nodesdeenergize relay 46, or the antinodes energize relay ll. Either thedeenergization of relay 46 or the energization of relay 4? results inthe actuation of relay 38 with the consequential supply of heatingcurrent to the antenna.

When sleet or ice forms on the antenna, standing wave voltages, such asthose illustrated in Fig. 5, are produced on the line 32. The existenceof nodes or antinodes of these standing wave voltages results in achange in the electromotive force impressed on the control electrodes ofdevices 43 and 4!. If the nodes are at or near the point of the line 32at which devices 43 and M are connected, a decrease in current of theanode circuit which deenergizes relay 4% results, while when theantinodes are at or near the point, an increase in current in the anodecircuit which energizes relay d? is produced. Relay 33 is actuated andheating current passes from the source 35 through the transformer 38,line 54, line 32 to the antenna 3|. When the sleet has melted oi? thewires of the antenna 3|, the line voltage returns to normal or thatrepresented by the dotted line in Fig. 4.. The voltage impressed uponthe control electrode of devices 4| and 40 is then such that relay 43 isenergized and relay 41 is deenergized. The armature of relay 38disengages from its contact and the source of heating current isdisconnected from the line 32.

Fig. 3 shows a system for supplying a heating current from a directcurrent source to an antenna and for disabling the radio transmitter ofthe system when standing waves are produced on the line between theradio transmitter and the antenna. The manner of supplying the heatingcturent and the apparatus employed for this purpose are similar to thesystem shown in Fig. 2, In addition to supplying the antenna withheating current when standing waves are produced on the line between theradio transmitter and antenna,

electromagnetic means are actuated to disable the radio transmitter. Anindicator, visual or acoustical, or both, is also actuated to apprisethe operator at the transmitting station of the production of standingwaves on the line. The disability of the radio transmitter and theindication of the production of standing waves on the line areespecially advantageous in that abnormalities other than the formationof sleet on the antenna, such as the breaking of the line, which producestanding waves are quickly detected.

The parts of the system, the operation and functions of which are thesame as those shown in Fig. 2 have the same numerals in Fig. 3. Thedescription of these parts together with their function in the system isnot repeated at this point. Instead of the cathode current supply shownin Fig. 2, a unidirectional current source 5'5 supplies heating currentto the cathodes of devices 40 and 4|.

If standing waves are produced on the line 32 the change ofelectromotive force resulting from the standing waves impressed on thecontrol electrodes of devices 43 and ll causes the deenergization ofrelay 43 or the energization of relay 4'! in a manner similar to thatfor the sys-- tem shown in Fig. 2. If the point of connection of thedevices 43 and ii to the line 32 is at or near a node of the standingwaves, a decrease in current in the anode circuit resuits whichdeenergizes relay 45, while if the point of connection is at or near anantinode of the standing wave, an increase in anode current is producedwhich energizes relay il. Deenergization of relay 45 or the energizationof relay i'l results in the energization of relay 38.

One of the armatures of relay 33 with its associated make contactcompletes a circuit for supplying direct current from a direct currentsource 6|! to the antenna 3|. The circuit for supplying heating currentto the antenna from the direct current source includes the directcurrent source 60, one arm of a double throw switch 32, one side of line54, one side of line 32, antenna 3|, half wave length loop I8, antenna 3l the other side of line 32, the other side of line 5 3, currentregulating resistance 3?, the other arm of the double throw switch 3|,contact and armature of relay 33 to the direct current source 63.

Another armature of the relay 38 with its associated contact completes acircuit for operating a visual or acoustical indicator. The indicatormay be an electric lamp 32 or a bell 63. Both the lamp 62 and the bell83 are supplied with current from the direct current source (it, thebell through a current limiting resistance 64. When the relay 38 isenergized the engagement of one of the armatures with its associatedcontact completes a circuit for the illumination of the lamp 62 and theactuation of the bell 33.

Another armature of the relay 33 with its associated contact completes acircuit for the energization of a relay 65 from direct current source60. The power for the radio transmitter is supplied from the source 60through the armature and contact of the relay 35. When the relay 38 isenergized the engagement of one of the armatures with its associatedmake contact results in the actuation of relay 65, whereby the directcurrent source 63 is disconnected from the radio transmitter to disablethe transmitter.

When standing waves are produced on the line 32 relay 46 is deenergized,or relay .41 is energized. Relay 38 is actuated, resulting in theenagement of its three armatures with their contacts. Heating currentpasses from the direct current source 60 to the antenna 3|. The lamp 62is. illuminated and the bell 63 rings. Relay E5 is energized to removethe direct current source supplying the radio transmitter. The removalof the direct current source 6!] disables the transmitter. If for anyreason, the supply of heating current to the antenna is not desired thecircuit from the direct current source 60 to the antenna 3! may beopened by means of the double throw manually operated switch 6|. If, forexample, the sleet melting system is not required and it is desired todetect any abnormality which produces standing waves on the line or todisable the radio transmitter when these abnormalities occur, the sleetmelting system may be removed by the switch 6 I.

While preferred embodiments of this invention have been illustrated anddescribed, various modifications therein may be made without departingfrom the scope of the appended claims.

What is claimed is:

1. An electrical system comprising an antenna, a source of heatingenergy, and means actuated by the formation of a frozen deposit on saidsystem for connecting said source of energy to said antenna and fordiscontinuing the supply of energy only after said deposit has melted.

2. In a radio system, an antenna, a source of high frequency energy, aline connected between said high frequency source and said antenna, asource of heating energy and means responsive to the existence ofstanding waves on said line for supplying said antenna with heatingenergy from said source of heating energy.

3. In combination, an antenna, a source of high frequency energytherefor, a line connecting said high frequency energy source with saidantenna, a source of heating energy associated with said antenna andmeans responsive to changes in the impedance relationship between saidline and said antenna for supplying energy from said source of heatingenergy to said antenna.

4. In a radio system, an antenna, a source of heating energy, a gap incooperative relation with said antenna whereby a frozen deposit isformed in said gap when sleet is present on said antenna and meansresponsive to the presence of a frozen deposit in said gap for supplyingenergy from said source to said antenna.

5. An electrical system, a load, a source of current, a line connectingsaid source tosaid load, and means responsive to standing waves on saidline to disable said source.

6. In a radio system, an antenna, a source of high frequency current, aline connecting said source to said antenna, means to indicateacoustically the existence of standing waves on said line, and meansresponsive to standing waves on said line to disable said source.

'7. In a radio system, an antenna, a source of high frequency current, aline connecting said source to said antenna, means to indicate theexistence of standing waves on said line, means responsive to standingwaves on said line to disable said source, and means responsive tostanding waves on said line to supply heating current to said antenna.

8. In a radio system, an antenna, a radio transmitter, a source ofcurrent for said transmitter, a line connecting said transmitter to saidantenna, means to indicate acoustically the existence of standing waveson said line, means responsive to standing waves on said line to removesaid source from said transmitter whereby said transmitter is disabled,and means responsive to standing waves on said line to supply heatingcurrent to said antenna.

9. In a radio system, an antenna, a source of high frequency current, aline connecting said source to said antenna, a source of heating energy,and means responsive to the existence of standing waves on said line forsupplying energy from said heating source to said antenna.

10. In a radio system, an antenna, a source of high frequency current, aline connecting said source to said antenna, a source of heatingcurrent, and means responsive to the existence of standing waves on saidline for passing a current from said source of heating current throughsaid antenna.

11. A method of melting sleet on a radio antenna comprising supplyingheating energy to an antenna in response to the existence of standingwaves on the line connecting the transmitter and antenna of the system.

12. A method of removing a frozen deposit from an antenna of a radiosystem comprising supplying heating energy to the antenna in re sponseto the existence of standing waves on the line connecting thetransmitter and antenna of the system and discontinuing the supply ofsaid energy in response to the non-existence of standing waves on saidline.

13. In a radio system, an antenna, a source of high frequency current, aline connecting said source to said antenna, space discharge devicesconnected to said line and responsive to the existence of standing waveson said line, an output circuit connected to said devices, and meanscontrolled by the current in said output circuit of said space dischargedevices for indicating the existence of standing waves on said line.

14. A radio system comprising an antenna, a source of heating energy,and means responsive to the formation of a frozen deposit in a part ofsaid system for connecting said source to said antenna and formaintaining the connection during the existence of said deposit.

15. An electrical system, a source of heating energy, and control meansdirectly actuated by every change in the impedance of a part of saidsystem for connecting said source to said system.

16. An electrical system comprising a plurality of exposed conductors, asource of heating energy, means directly responsive, irrespective of thetemperature of said conductors, to the presence of a frozen deposit onone of said conductors for supplying energy from said source to at leastone of said conductors during the entire period said deposit exists andimmediately discontinuing the supply upon removal of said deposit.

FRANCIS F. MERRIAM.

